JEEP GRAND CHEROKEE 2002 WJ / 2.G Workshop Manual

Fig. 261 Regulator Valve in DRIVE Position
Fig. 262 Regulator Valve in REVERSE Position
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VALVE BODY (Continued)

KICKDOWN VALVE
When the throttle valve is as far over to the left as
it can go, the maximum line pressure possible will
enter the throttle pressure circuit. In this case, throt-
tle pressure will equal line pressure. With the kick-
down valve (Fig. 263) pushed into the bore as far as
it will go, fluid initially flows through the annular
groove of the 2-3 shift valve (which will be in the
direct drive position to the right).After passing the annular groove, the fluid is
routed to the spring end of the 2-3 shift valve. Fluid
pressure reacting on the area of land #1 overcomes
governor pressure, downshifting the 2-3 shift valve
into the kickdown, or second gear stage of operation.
The valve is held in the kickdown position by throttle
pressure routed from a seated check ball (#2). Again,
if vehicle speed is low enough, throttle pressure will
also push the 1-2 shift valve left to seat its governor
plug, and downshift to drive breakaway.
Fig. 263 Kickdown Valve-Wide Open Throttle
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VALVE BODY (Continued)

KICKDOWN LIMIT VALVE
The purpose of the limit valve is to prevent a 3-2
downshift at higher speeds when a part-throttle
downshift is not desirable. At these higher speeds
only a full throttle 3-2 downshift will occur. At low
road speeds (Fig. 264) the limit valve does not come
into play and does not affect the downshifts. As the
vehicle's speed increases (Fig. 265), the governor
pressure also increases. The increased governor pres-
sure acts on the reaction area of the bottom land ofthe limit valve overcoming the spring force trying to
push the valve toward the bottom of its bore. This
pushes the valve upward against the spring and bot-
toms the valve against the top of the housing. With
the valve bottomed against the housing, the throttle
pressure supplied to the valve will be closed off by
the bottom land of the limit valve. When the supply
of throttle pressure has been shut off, the 3-2 part
throttle downshift plug becomes inoperative, because
no pressure is acting on its reaction area.
Fig. 264 Kickdown Limit Valve-Low Speeds
Fig. 265 Kickdown Limit Valve-High Speeds
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VALVE BODY (Continued)

1-2 SHIFT VALVE
The 1-2 shift valve assembly (Fig. 266), or mecha-
nism, consists of: the 1-2 shift valve, governor plug,
and a spring on the end of the valve. After the man-
ual valve has been placed into a forward gear range,
line pressure is directed to the 1-2 shift valve. As the
throttle is depressed, throttle pressure is applied to
the right side of the 1-2 shift valve assembly. With
throttle pressure applied to the right side of the
valve, there is now both spring pressure and throttle
pressure acting on the valve, holding it against the
governor plug. As the vehicle begins to move and
build speed, governor pressure is created and is
applied to the left of the valve at the governor plug.
When governor pressure builds to a point where it
can overcome the combined force of the spring and
throttle pressure on the other side of the valve, the
valve will begin to move over to the right. As the
valve moves to the right, the middle land of the valve
will close off the circuit supplying the throttle pres-
sure to the right side of the valve. When the throttlepressure is closed off, the valve will move even far-
ther to the right, allowing line pressure to enter
another circuit and energize the front servo, applying
the front band (Fig. 267).
The governor plug serves a dual purpose:
²It allows the shift valves to move either left or
right, allowing both upshifts and downshifts.
²When in a manual selection position, it will be
hydraulically ªblockedº into position so no upshift can
occur.
The physical blocking of the upshift while in the
manual ª1º position is accomplished by the directing
of line pressure between both lands of the governor
plug. The line pressure reacts against the larger land
of the plug, pushing the plug back against the end
plate overcoming governor pressure. With the combi-
nation of the line pressure and spring pressure, the
valve cannot move, preventing any upshift.
Fig. 266 1-2 Shift Valve-Before Shift
Fig. 267 1-2 Shift Valve-After Shift
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VALVE BODY (Continued)

1-2 SHIFT CONTROL VALVE
It contains a valve with four lands and a spring. It
is used as both a ªrelayº and ªbalancedº valve.
The valve has two specific operations (Fig. 268):
²Aid in quality of the 1-2 upshift.
²Aid in the quality and timing of the 3-2 kick-
down ranges.
When the manual valve is set to the DRIVE posi-
tion and the transmission is in the first or second
gear range, 1-2 shift control or ªmodulated throttle
pressureº is supplied to the middle of the accumula-
tor piston by the 1-2 shift control valve. During the1-2 upshift, this pressure is used to control the kick-
down servo apply pressure that is needed to apply
the kickdown and accumulator pistons. Thus, the 1-2
shift point is ªcushionedº and the quality is
improved. During a WOT kickdown, kickdown pres-
sure is applied between the kickdown valve and the
1-2 shift control valve. This additional pressure is
directed to the 1-2 shift control's spring cavity, add-
ing to the spring load on the valve. The result of this
increased ªmodulatedº throttle pressure is a firmer
WOT upshift.
Fig. 268 1-2 Shift Control Valve
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VALVE BODY (Continued)

2-3 SHIFT VALVE
The 2-3 shift valve mechanism (Fig. 269) consists
of the 2-3 shift valve, governor plug and spring, and
a throttle plug. After the 1-2 shift valve has com-
pleted its operation and applied the front band, line
pressure is directed to the 2-3 shift valve through theconnecting passages from the 1-2 shift valve. The line
pressure will then dead±end at land #2 until the 2-3
valve is ready to make its shift. Now that the vehicle
is in motion and under acceleration, there is throttle
pressure being applied to the spring side of the valve
and between lands #3 and #4.
Fig. 269 2-3 Shift Valve-Before Shift
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VALVE BODY (Continued)

As vehicle speed increases, governor pressure
increases proportionately, until it becomes great
enough to overcome the combined throttle and spring
pressure on the right side of the valve. Since the
throttle pressure end of the 2-3 shift valve is larger
in diameter than the 1-2 shift valve, the 2-3 shift will
always happen at a greater speed than the 1-2 shift.
When this happens, the governor plug is forced
against the shift valve moving it to the right. The
shift valve causes land #4 to close the passage sup-
plying throttle pressure to the 2-3 shift valve. With-
out throttle pressure present in the circuit now, the
governor plug will push the valve over far enough to
bottom the valve in its bore. This allows land #2 to
direct line pressure to the front clutch.After the shift (Fig. 270), line pressure is directed
to the land between the shift valve and the governor
plug, and to the release side of the kickdown servo.
This releases the front band and applies the front
clutch, shifting into third gear or direct drive. The
rear clutch remains applied, as it has been in the
other gears. During a manual ª1º or manual ª2º gear
selection, line pressure is sent between the two lands
of the 2-3 governor plug. This line pressure at the
governor plug locks the shift valve into the second
gear position, preventing an upshift into direct drive.
The theory for the blocking of the valve is the same
as that of the 1-2 shift valve.
Fig. 270 2-3 Shift Valve-After Shift
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VALVE BODY (Continued)

3-4 SHIFT VALVE
The PCM energizes the overdrive solenoid during
the 3-4 upshift (Fig. 271). This causes the solenoid
check ball to close the vent port allowing line pres-
sure from the 2-3 shift valve to act directly on the 3-4
upshift valve. Line pressure on the 3-4 shift valve
overcomes valve spring pressure moving the valve to
the upshift position (Fig. 272). This action exposes
the feed passages to the 3-4 timing valve, 3-4 quick
fill valve, 3-4 accumulator, and ultimately to the
overdrive piston.
3-4 TIMING VALVE
The 3-4 timing valve is moved by line pressure
coming through the 3-4 shift valve (Fig. 272). After
the shift, the timing valve holds the 2-3 shift valve in
an upshift position. The purpose is to prevent the 2-3
valve from downshifting before the 3-4 valve (Fig.
271).
3-4 QUICK FILL VALVE
The 3-4 quick fill valve provides faster engagement
of the overdrive clutch during 3-4 upshifts. The valve
temporarily bypasses the clutch piston feed orifice at
the start of a 3-4 upshift (Fig. 271). This exposes a
larger passage into the piston retainer resulting in a
much faster clutch fill and apply sequence. The quick
fill valve does not bypass the regular clutch feed ori-
fice throughout the 3-4 upshift. Instead, once a pre-
determined pressure develops within the clutch, the
valve closes the bypass (Fig. 272). Clutch fill is then
completed through the regular feed orifice.
Fig. 271 3-4 Shift Valve Before Shift
Fig. 272 3-4 Shift Valve After Shift
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VALVE BODY (Continued)

THROTTLE VALVE
In all gear positions the throttle valve (Fig. 273) is
being supplied with line pressure. The throttle valve
meters and reduces the line pressure that now
becomes throttle pressure. The throttle valve is
moved by a spring and the kickdown valve, which is
mechanically connected to the throttle. The larger
the throttle opening, the higher the throttle pressure
(to a maximum of line pressure). The smaller the
throttle opening, the lower the throttle pressure (to a
minimum of zero at idle). As engine speed increases,
the increase in pump speed increases pump output.
The increase in pressure and volume must be regu-
lated to maintain the balance within the transmis-
sion. To do this, throttle pressure is routed to the
reaction area on the right side of the throttle pres-
sure plug (in the regulator valve).
The higher engine speed and line pressure would
open the vent too far and reduce line pressure too
much. Throttle pressure, which increases with engine
speed (throttle opening), is used to oppose the move-
ment of the pressure valve to help control the meter-
ing passage at the vent. The throttle pressure is
combined with spring pressure to reduce the force of
the throttle pressure plug on the pressure valve. The
larger spring at the right closes the regulator valvepassage and maintains or increases line pressure.
The increased line pressure works against the reac-
tion area of the line pressure plug and the reaction
area left of land #3 simultaneously moves the regu-
lator valve train to the right and controls the meter-
ing passage.
The kickdown valve, along with the throttle valve,
serve to delay upshifts until the correct vehicle speed
has been reached. It also controls downshifts upon
driver demand, or increased engine load. If these
valves were not in place, the shift points would be at
the same speed for all throttle positions. The kick-
down valve is actuated by a cam connected to the
throttle. This is accomplished through either a link-
age or a cable. The cam forces the kickdown valve
toward the throttle valve compressing the spring
between them and moving the throttle valve. As the
throttle valve land starts to uncover its port, line
pressure is ªmeteredº out into the circuits and viewed
as throttle pressure. This increased throttle pressure
is metered out into the circuits it is applied to: the
1-2 and 2-3 shift valves. When the throttle pressure
is high enough, a 3-2 downshift will occur. If the
vehicle speed is low enough, a 2-1 downshift will
occur.
Fig. 273 Throttle Valve
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VALVE BODY (Continued)

SWITCH VALVE
When the transmission is in Drive Second before
the TCC application occurs (Fig. 274), the pressure
regulator valve is supplying torque converter pres-
sure to the switch valve. The switch valve directs
this pressure through the transmission input shaft,
into the converter, through the converter, back outbetween the input shaft and the reaction shaft, and
back up to the switch valve. From the switch valve,
the fluid pressure is directed to the transmission
cooler, and lubrication pressure returns from the
cooler to lubricate different portions of the transmis-
sion.
Fig. 274 Switch Valve-Torque Converter Unlocked
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VALVE BODY (Continued)